Android Marshmallow MPA44G Developer Preview 3 is now available for Nexus 9. You will be receiving this last preview built over-the-air in the coming few days. However, if you want to manually flash Android MPA4GG on Nexus 9, following guide will help you with the process. It is further added on with the steps to root your Nexus 9 on Android Marshmallow MPA44G developer preview.